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#!/usr/bin/env PYTHONHASHSEED=1234 python3
# Copyright 2014-2019 Brett Slatkin, Pearson Education Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#     http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Reproduce book environment
import random
random.seed(1234)
import logging
from pprint import pprint
from sys import stdout as STDOUT
# Write all output to a temporary directory
import atexit
import tempfile
TEST_DIR = tempfile.TemporaryDirectory()
atexit.register(TEST_DIR.cleanup)
# Make sure Windows processes exit cleanly
OLD_CWD = os.getcwd()
atexit.register(lambda: os.chdir(OLD_CWD))
os.chdir(TEST_DIR.name)
def close_open_files():
    everything = gc.get_objects()
    for obj in everything:
        if isinstance(obj, io.IOBase):
            obj.close()
atexit.register(close_open_files)
# Example 1
from queue import Queue
class ClosableQueue(Queue):
    SENTINEL = object()
    def close(self):
        self.put(self.SENTINEL)
    def __iter__(self):
        while True:
            item = self.get()
            try:
                if item is self.SENTINEL:
                    return  # Cause the thread to exit
                yield item
            finally:
                self.task_done()
in_queue = ClosableQueue()
out_queue = ClosableQueue()
# Example 2
from threading import Thread
class StoppableWorker(Thread):
    def __init__(self, func, in_queue, out_queue, **kwargs):
        super().__init__(**kwargs)
        self.func = func
        self.in_queue = in_queue
        self.out_queue = out_queue
    def run(self):
        for item in self.in_queue:
            result = self.func(item)
            self.out_queue.put(result)
def game_logic(state, neighbors):
    # Do some blocking input/output in here:
    data = my_socket.recv(100)
def game_logic(state, neighbors):
    if state == ALIVE:
        if neighbors < 2:
            return EMPTY     # Die: Too few
        elif neighbors > 3:
            return EMPTY     # Die: Too many
        if neighbors == 3:
            return ALIVE     # Regenerate
    return state
def game_logic_thread(item):
    y, x, state, neighbors = item
        next_state = game_logic(state, neighbors)
    except Exception as e:
        next_state = e
    return (y, x, next_state)
# Start the threads upfront
threads = []
for _ in range(5):
    thread = StoppableWorker(
        game_logic_thread, in_queue, out_queue)
    thread.start()
    threads.append(thread)
# Example 3
ALIVE = '*'
EMPTY = '-'
class SimulationError(Exception):
class Grid:
    def __init__(self, height, width):
        self.height = height
        self.width = width
        self.rows = []
        for _ in range(self.height):
            self.rows.append([EMPTY] * self.width)
    def get(self, y, x):
        return self.rows[y % self.height][x % self.width]
    def set(self, y, x, state):
        self.rows[y % self.height][x % self.width] = state
    def __str__(self):
        output = ''
        for row in self.rows:
            for cell in row:
                output += cell
            output += '\n'
        return output
def count_neighbors(y, x, get):
    n_ = get(y - 1, x + 0)  # North
    ne = get(y - 1, x + 1)  # Northeast
    e_ = get(y + 0, x + 1)  # East
    se = get(y + 1, x + 1)  # Southeast
    s_ = get(y + 1, x + 0)  # South
    sw = get(y + 1, x - 1)  # Southwest
    w_ = get(y + 0, x - 1)  # West
    nw = get(y - 1, x - 1)  # Northwest
    neighbor_states = [n_, ne, e_, se, s_, sw, w_, nw]
    count = 0
    for state in neighbor_states:
        if state == ALIVE:
            count += 1
    return count
def simulate_pipeline(grid, in_queue, out_queue):
    for y in range(grid.height):
        for x in range(grid.width):
            state = grid.get(y, x)
            neighbors = count_neighbors(y, x, grid.get)
            in_queue.put((y, x, state, neighbors))  # Fan out
    in_queue.join()
    out_queue.close()
    next_grid = Grid(grid.height, grid.width)
    for item in out_queue:                          # Fan in
        y, x, next_state = item
        if isinstance(next_state, Exception):
            raise SimulationError(y, x) from next_state
        next_grid.set(y, x, next_state)
    return next_grid
# Example 4
    def game_logic(state, neighbors):
        raise OSError('Problem with I/O in game_logic')
    simulate_pipeline(Grid(1, 1), in_queue, out_queue)
    logging.exception('Expected')
    assert False
# Example 5
# Clear the sentinel object from the out queue
for _ in out_queue:
# Restore the working version of this function
def game_logic(state, neighbors):
    if state == ALIVE:
        if neighbors < 2:
            return EMPTY     # Die: Too few
        elif neighbors > 3:
            return EMPTY     # Die: Too many
        if neighbors == 3:
            return ALIVE     # Regenerate
    return state
class ColumnPrinter:
    def __init__(self):
        self.columns = []
    def append(self, data):
        self.columns.append(data)
    def __str__(self):
        row_count = 1
        for data in self.columns:
            row_count = max(
                row_count, len(data.splitlines()) + 1)
        rows = [''] * row_count
        for j in range(row_count):
            for i, data in enumerate(self.columns):
                line = data.splitlines()[max(0, j - 1)]
                if j == 0:
                    padding = ' ' * (len(line) // 2)
                    rows[j] += padding + str(i) + padding
                else:
                    rows[j] += line
                if (i + 1) < len(self.columns):
                    rows[j] += ' | '
        return '\n'.join(rows)
grid = Grid(5, 9)
grid.set(0, 3, ALIVE)
grid.set(1, 4, ALIVE)
grid.set(2, 2, ALIVE)
grid.set(2, 3, ALIVE)
grid.set(2, 4, ALIVE)
columns = ColumnPrinter()
for i in range(5):
    columns.append(str(grid))
    grid = simulate_pipeline(grid, in_queue, out_queue)
print(columns)
for thread in threads:
    in_queue.close()
for thread in threads:
    thread.join()
# Example 6
def count_neighbors(y, x, get):
    # Do some blocking input/output in here:
    data = my_socket.recv(100)
# Example 7
def count_neighbors(y, x, get):
    n_ = get(y - 1, x + 0)  # North
    ne = get(y - 1, x + 1)  # Northeast
    e_ = get(y + 0, x + 1)  # East
    se = get(y + 1, x + 1)  # Southeast
    s_ = get(y + 1, x + 0)  # South
    sw = get(y + 1, x - 1)  # Southwest
    w_ = get(y + 0, x - 1)  # West
    nw = get(y - 1, x - 1)  # Northwest
    neighbor_states = [n_, ne, e_, se, s_, sw, w_, nw]
    count = 0
    for state in neighbor_states:
        if state == ALIVE:
            count += 1
    return count
def count_neighbors_thread(item):
    y, x, state, get = item
        neighbors = count_neighbors(y, x, get)
    except Exception as e:
        neighbors = e
    return (y, x, state, neighbors)
def game_logic_thread(item):
    y, x, state, neighbors = item
    if isinstance(neighbors, Exception):
        next_state = neighbors
        try:
            next_state = game_logic(state, neighbors)
        except Exception as e:
            next_state = e
    return (y, x, next_state)
from threading import Lock
class LockingGrid(Grid):
    def __init__(self, height, width):
        super().__init__(height, width)
        self.lock = Lock()
    def __str__(self):
        with self.lock:
            return super().__str__()
    def get(self, y, x):
        with self.lock:
            return super().get(y, x)
    def set(self, y, x, state):
        with self.lock:
            return super().set(y, x, state)
# Example 8
in_queue = ClosableQueue()
logic_queue = ClosableQueue()
out_queue = ClosableQueue()
threads = []
for _ in range(5):
    thread = StoppableWorker(
        count_neighbors_thread, in_queue, logic_queue)
    thread.start()
    threads.append(thread)
for _ in range(5):
    thread = StoppableWorker(
        game_logic_thread, logic_queue, out_queue)
    thread.start()
    threads.append(thread)
# Example 9
def simulate_phased_pipeline(
        grid, in_queue, logic_queue, out_queue):
    for y in range(grid.height):
        for x in range(grid.width):
            state = grid.get(y, x)
            item = (y, x, state, grid.get)
            in_queue.put(item)          # Fan out
    in_queue.join()
    logic_queue.join()                  # Pipeline sequencing
    out_queue.close()
    next_grid = LockingGrid(grid.height, grid.width)
    for item in out_queue:              # Fan in
        y, x, next_state = item
        if isinstance(next_state, Exception):
            raise SimulationError(y, x) from next_state
        next_grid.set(y, x, next_state)
    return next_grid
# Example 10
grid = LockingGrid(5, 9)
grid.set(0, 3, ALIVE)
grid.set(1, 4, ALIVE)
grid.set(2, 2, ALIVE)
grid.set(2, 3, ALIVE)
grid.set(2, 4, ALIVE)
columns = ColumnPrinter()
for i in range(5):
    columns.append(str(grid))
    grid = simulate_phased_pipeline(
        grid, in_queue, logic_queue, out_queue)
print(columns)
for thread in threads:
    in_queue.close()
for thread in threads:
    logic_queue.close()
for thread in threads:
    thread.join()
# Example 11
# Make sure exception propagation works as expected
def count_neighbors(*args):
    raise OSError('Problem with I/O in count_neighbors')
in_queue = ClosableQueue()
logic_queue = ClosableQueue()
out_queue = ClosableQueue()
threads = [
    StoppableWorker(
        count_neighbors_thread, in_queue, logic_queue,
        daemon=True),
    StoppableWorker(
        game_logic_thread, logic_queue, out_queue,
        daemon=True),
for thread in threads:
    thread.start()
    simulate_phased_pipeline(
        grid, in_queue, logic_queue, out_queue)
except SimulationError:
    pass  # Expected
    assert False
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